Here's another interesting paper [1] on that topic. It shows that synthetically blurred images are significantly more realistic if they're based on recovered radiance maps (HDR).
If I understand correctly, you're looking for a simplified RAW image editor? Many digital cameras allow storing RAW images alongside JPEG. The viewer can then load the RAW images into any (web-based) image viewer/editor that supports RAW format and have full control over tone mapping.
The tool interface needs to be simplified to make it a better fit for the use-case you present but I don't see computing power as a bottleneck.
Of course they'd still be limited by the dynamic range of the camera. This can also be resolved by calculating irradiance map based on multiple RAW images taken with different exposure times.